(a) Field of the Invention
The present invention relates to a method for blast cleaning using ilmenite tailing particles as impact abrasive material.
(b) Description of Prior Art
Due to its high hardness and low cost, silica sand has been used extensively for impact abrasion. It is, however, very brittle with most grains disintegrating on impact, causing excessive levels of siliceous dust which is a major health hazard and causes serious environmental pollution. Consequently, it has been banned as impact abrasive material in most countries around the world. Considerable research has been done in the last twenty (20) years to find an impact abrasive material as hard as silica sand and that respects North American norms for dust emissions. Furthermore, the impact abrasive material must be cost effective. Usually characterized by a high hardness, mineral slags such as those containing copper, nickel, iron (JP 59053613), and alloys (JP 62039683) have been used. These slags are quenched from molten state with cold water and crushed and/or grinded, giving each particle a glassy brittle structure with distinct fracture lines. Upon blasting impact, the slag particle shatters into minute particles and become airborne due to their small size and low specific gravity, resulting in the generation of high dust levels. Moreover, these slags, especially the copper slag and nickel slag, are waste products of the metals refining industry and frequently contain unacceptable levels of toxic heavy metals such as lead, copper, zinc, arsenic and cadmium, etc. Finally, slag crushing and/or grinding are energetically inefficient processes which increase the cost of impact abrasive materials. There therefore exists a need for a new impact abrasive material for blast cleaning which respects governmental norms for dust emissions and is cost efficient.